Figure 3.

Effect of TRα/T₃ on Nur77 transactivation in the promoter of steroidogenic enzyme genes. A, MA-10 cells were transfected with TRα expression plasmids and NBRE-Luc reporter construct in medium containing 5% charcoal-stripped serum. Cells were treated with 8Br-cAMP (0.5 mM) and T₃ (100 nM) after 24 hours of transfection and harvested for measurement of luciferase activity after an additional 24 hours. B–E, MA-10 cells were transfected with Nur77 expression plasmid (50 ng) and increasing amounts of TRα expression plasmid (20, 50, and 100 ng) (panel B), with increasing amounts of only TRα expression plasmid (20, 50, and 100 ng) (panel C) or with Nur77 expression plasmid (100 ng) and TRα expression plasmid (+: 100 ng, ++: 200 ng) (panels D and E), and the indicated reporter construct. Cells were treated with T₃ after 24 hours of transfection and harvested for measurement of luciferase activity after an additional 24 hours. In all panels, values are the means ± SEM of 3 independent experiments performed in duplicate. *, P < .05; **, P < .01; ***, P < .001.